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Understanding blue carbon storage and accumulation prior to engineering projects is essential for assessing the potential co-benefit of carbon storage for natural climate solutions. This study collected sediment cores from the western portion of Boundary Bay, Delta, British Columbia (BC), where implementation of a living dike pilot project is planned to alleviate impacts of sea level rise. Total carbon stocks were 10,034 ± 3,148 Mg C for the western 140 ha of marsh, with stocks averaging 83.3 ± 29.3 Mg C/ha (high marsh) and 39.3 ± 24.2 Mg C/ha (low marsh). Carbon accumulation rates (CARs) exhibited substantial variability, ranging from 19.5 to 454 g C/m2/yr (median 70.1 g C/m2/yr). Both stocks and accumulation rates were at least 45% lower than globally averaged estimates, likely due to the shallow depth and dominant vegetation type of the marsh. Despite historical modifications to the marsh, our study indicates that the western marsh has expanded by about 20% since 1930, which we estimate increased carbon stocks by about 1,549-1,698 Mg C. This study's quantification of carbon stocks and CARs is an important first step towards leveraging the co-benefit of salt marshes for improved management, restoration, and preservation. However, additional data are needed to document the greenhouse gas budgets for carbon accounting purposes, along with exploration of law and policy issues related to carbon stewardship in a multi-jurisdictional coastal environment. We outline subsequent research needed for salt marshes such as Boundary Bay to be included in voluntary carbon markets in British Columbia. [ABSTRACT FROM AUTHOR]

A comprehensive review of Holocene paleoenvironmental data has been prepared, providing the basis for evaluating natural variability in climate and ecosystem dynamics in the northern Columbia River basin. The paleoenvironmental record reveals four major climatic shifts and a number of less well-defined climatic changes throughout the Holocene. The major climate changes are (1) a cool or cold, late-glacial climate at the end of the last glaciation (>11 500 cal. year BP), (2) an interval of drought and maximum summer warmth during the early Holocene (ca. 10500 to 8000 cal. year BP), (3) a mid-Holocene trend towards a cooler, more moist climate (ca. 8000 to ca. 4000 cal. year BP), and (4) a relatively stable climate persisting from ca. 4000 cal. year BP until the arrival of European settlers. Air temperatures have warmed by about 1 °C over the past century. Minor climate events that are emerging as global in nature include Little Ice Age (1200–150 BP) conditions, and a late Holocene cool wet period (3500–2500 BP). These are observed in some study sites examined in this paper and may be related to large-scale cycles of 2800–2000 and 1500 years. A discussion of changing atmospheric circulation patterns, and the causes of long-term climatic change are included, together with a discussion of the implications of the paleoenvironmental record for understanding future climate, and the likely response of communities and ecosystems. [ABSTRACT FROM AUTHOR]

Late-glacial sediments at Mike Lake in the Fraser Lowland of southwestern British Columbia shed light on the timing and significance of the Younger Dryas and Sumas events on the west coast of Canada. Five pollen zones span the period from about 11 700 to 9700 radiocarbon years before present (yr BP) or 13 700 to 11 200 calibrated calendar years before present (cal BP). Climate during this interval is inferred to have ranged from cool continental to warm and dry. Changes in pollen assemblages, lithology, and loss on ignition in Mike Lake sediments deposited prior to 11 000 yr BP (13 000 cal BP) may signal the Sumas glacial advance, which has been dated elsewhere in the Fraser Lowland to this time. Palynologic and sedimentological data indicate that there was much climatic and ecological variability in southwestern British Columbia during the Younger Dryas chronozone. Detrended correspondence analysis of modern pollen from lake-sediment surface samples collected throughout British Columbia is used to compare Mike Lake fossil pollen assemblages to modern vegetation zones. The inferred vegetation assemblage during most of the Younger Dryas chronozone indicates a progressively warming climate with a cool interval between 10 400 and 10 000 yr BP. The pollen assemblage in this interval is similar to that of present subalpine forests on the west coast of Canada. The cooling coincides with the later part of the Younger Dryas chronozone and occurred too late to be the driving mechanism for the final Sumas advance, which peaked around 11 300 14C yr BP (13 200 cal BP). [Copyright &y& Elsevier]